Noise reduction for total field magnetometer measurements

Abstract

A method and apparatus for a streamer having a total field magnetometer (“TFM”). A streamer includes a plurality of TFMs in proximity with one another and distributed symmetrically about an axis of the streamer. A streamer includes a first subset of TFMs in a streamer section and in proximity with one another; a second subset in the streamer section and in proximity with one another; wherein the first subset is not in proximity with the second subset. A method includes towing a streamer through a body of water, the streamer comprising first and second TFMs; acquiring magnetic data with the first and the second TFMs; and reducing noise in the data based on at least one of: averaging data from the first and the second TFMs; filtering data from the first and the second TFMs; estimating motion of the first TFM; and estimating rotation of the first TFM.

The invention claimed is: 
     
       1. A method comprising:
 towing a streamer through a body of water, wherein the streamer comprises a first total field magnetometer and a second total field magnetometer; 
 acquiring total magnetic field data with the first and the second total field magnetometers; 
 reducing noise in the total magnetic field data based on at least one of:
 averaging data from the first and the second total field magnetometers; 
 filtering data from the first and the second total field magnetometers; 
 estimating motion of the first total field magnetometer; and 
 estimating rotation of the first total field magnetometer; 
 
 acquiring data with a plurality of total field magnetometers, wherein the plurality of total field magnetometers are:
 in longitudinal proximity with one another; and 
 distributed symmetrically about an axis of the streamer; and 
 
 at least one of:
 averaging data from the plurality of total field magnetometers to approximate a total magnetic field measurement at a point in longitudinal proximity with the plurality of total field magnetometers; 
 filtering data from the plurality of total field magnetometers to remove directional effects; and 
 estimating a magnetic field gradient at the point. 
 
 
     
     
       2. The method of  claim 1 , wherein the noise comprises at least one of:
 motion noise; 
 twist noise; 
 electromagnetic interference; and 
 directional effects. 
 
     
     
       3. The method of  claim 1 , wherein an inertial measurement unit that is collocated with the first total field magnetometer is used to estimate the motion or the rotation. 
     
     
       4. The method of  claim 3 , wherein the reducing noise comprises:
 estimating motion of the first total field magnetometer based on the inertial measurement unit data; 
 estimating motion-noise based on the estimated motion; and 
 correcting the total magnetic field data based on the estimated motion-noise. 
 
     
     
       5. The method of  claim 1 , further comprising:
 acquiring survey data with electromagnetic sensors on the streamer; and 
 reducing noise in the survey data based on the total magnetic field data. 
 
     
     
       6. The method of  claim 5 , further comprising jointly inverting the survey data and the total magnetic field data to produce a geophysical data product. 
     
     
       7. A method comprising:
 towing a streamer through a body of water, wherein the streamer comprises a first total field magnetometer and a second total field magnetometer; 
 acquiring total magnetic field data with the first and the second total field magnetometers; 
 reducing noise in the total magnetic field data based on at least one of:
 averaging data from the first and the second total field magnetometers; 
 filtering data from the first and the second total field magnetometers; 
 estimating motion of the first total field magnetometer; and 
 estimating rotation of the first total field magnetometer; 
 
 acquiring data with a plurality of total field magnetometers, wherein:
 a first subset of the plurality of total field magnetometers are contained within a first streamer section and are in longitudinal proximity with one another; 
 a second subset of the plurality of total field magnetometers are contained within the first streamer section and are in longitudinal proximity with one another; and 
 the first subset is not in longitudinal proximity with the second subset; 
 
 averaging data from the first subset with data from the second subset; and 
 attenuating effects in the total magnetic field data from motion that is local to the first streamer section based on the averaging. 
 
     
     
       8. The method of  claim 7 , wherein the noise comprises at least one of:
 motion noise; 
 twist noise; 
 electromagnetic interference; and 
 directional effects. 
 
     
     
       9. The method of  claim 7 , wherein an inertial measurement unit that is collocated with the first total field magnetometer is used to estimate the motion or the rotation. 
     
     
       10. The method of  claim 9 , wherein the reducing noise comprises:
 estimating motion of the first total field magnetometer based on the inertial measurement unit data; 
 estimating motion-noise based on the estimated motion; and 
 correcting the total magnetic field data based on the estimated motion-noise. 
 
     
     
       11. The method of  claim 7 , further comprising:
 acquiring survey data with electromagnetic sensors on the streamer; and 
 reducing noise in the survey data based on the total magnetic field data. 
 
     
     
       12. The method of  claim 11 , further comprising jointly inverting the survey data and the total magnetic field data to produce a geophysical data product.